STRUCTURE AND CLASSIFICATION OF THE ARTHROPODA. 525 



The result of the knowledge gained in the last quarter of 

 the nineteenth century has been to discredit altogether the 

 group Vermes^ thus set up and so largely accepted by German 

 writers even at the present day. We have, in fact, returned. 

 very nearly to Cuvier's conception of agreat division or branch, 

 which he called Articulata, including the Arthropoda and the 

 Cha3topoda (the latter equivalent to the Annelides of Lamarck, 

 a name adopted by Cuvier), and differing from it only by the 

 inclusion of the Rotifera. The name Articulata, introduced by 

 Cuvier, has not been retained by subsequent writers. The 

 same, or nearly the same assemblage of animals has been called 

 Entomozoaria by De Blainville (1882),Arthrozoaby Burmeister 

 (1843), Entomozoa or Annellata by Milne-Edwards (1855), 

 and Annulosa by M'Leay (1819), who was followed by Huxley 

 (1856). The character pointed to by all these terms is that 

 of a ring-like segmentation of the body. This, however, is 

 not the character to which we now ascribe the chief weight 

 as evidence of the genetic affinity and monophyletic (uni- 

 ancestral) origin of the Cha3topods, Rotifers, and Arthropods. 

 It is the existence in each ring of the body of a pair of hollow 

 lateral appendages or parapodia, moved by intrinsic 

 muscles and penetrated by blood-spaces, which is the leading 

 fact indicating the affinities of these great sub-phyla, and 

 uniting them as blood relations. The parapodia (tig. 7) of 

 the marine branchiate worms are the same things genetically 

 as the "legs" of Crustacea and insects (tigs. 9 and 10). 

 Hence the term Appeudiculata was introduced by Lankester 



cyclopsedia ol wliat was known and imagined about eartli, sea, sky, birds, 

 beasts, and fislies, wliicli for a Uiousand years was the authoritative source of 

 inlorniation on lliese matters, and was translated into every European tongue. 

 VVitli the revival ol' learning, however, first one and then another special study 

 became recognise<i — anatomy, botany, zoology, mineralogy, until at last the 

 great comprehensive ttrm Fhysiology was berel't ol' all its once-included 

 subject-matter exceptii;g the study ol' vitnl processes pursued by the more 

 learned members ol the medical profession. Professional tradition, and an 

 astute perception on their part of the omniscience suggested by the terms, 

 have left the medical men in English-speaking lands in undisturbed but 

 illogical possession of the words physiology, pliysic, and physician. 



